BubbleSort errors

Error   1   The best overloaded method match for 'Project_210.BubbleSorter.Sort(object[], Project_210.CompareOp)' has some invalid arguments    C:\Documents and Settings\Eddy Ho\Local Settings\Application Data\Temporary Projects\Project-210\Program.cs 67  13  Project-210
Error   2   Argument '2': cannot convert from 'Project_210.Program.CompareOp' to 'Project_210.CompareOp'    C:\Documents and Settings\Eddy Ho\Local Settings\Application Data\Temporary Projects\Project-210\Program.cs 67  42  Project-210

using System;
using System.Collections.Generic;
using System.Text;

namespace Project_210
{
    delegate bool CompareOp(object lhs, object rhs);

    class BubbleSorter
    {
        static public void Sort(object[] sortArray, CompareOp gtMethod)
        {
            for (int i = 0; i < sortArray.Length; i++)
            {
                for (int j = i + 1; j < sortArray.Length; j++)
                {
                    if (gtMethod(sortArray[j], sortArray[i]))
                    {
                        object temp = sortArray[i];
                        sortArray[i] = sortArray[j];
                        sortArray[j] = temp;
                    }
                }
            }
        }
    }

    class Employee
    {
        private string name;
        private decimal salary;

        public Employee(string name, decimal salary)
        {
                this.name = name;
                this.salary = salary;
         }
         public override string ToString()
         {
                return string.Format(name + " {0:C)", salary);
         }
         public static bool RhsIsGreater(object lhs, object rhs)
         {
                Employee empLhs = (Employee)lhs;
                Employee empRhs = (Employee)rhs;
                return (empRhs.salary > empLhs.salary) ? true : false;
         }
    }


    class Program
    {
        delegate bool CompareOp(object ihs, object rhs);

        static void Main(string[] args)
        {
            Employee[] employees =
                {
                    new Employee("Karli Watson",20000),
                    new Employee("Bill Gates",10000),
                    new Employee("Simon Robinson",25000),
                    new Employee("Mortime",(decimal)100000),
                    new Employee("Arabe Jones",20000),
                    new Employee("Avon from <code>'</code>;Black's 7'",50000)
                };
            CompareOp employeeCompareOp = new CompareOp(Employee.RhsIsGreater);
            BubbleSorter.Sort(employees, employeeCompareOp);

            for (int i = 0; i < employees.Length; i++)
                Console.WriteLine(employees[i].ToString());
        }
    }
}